In the remediation of facilities that had been used for the processing, storage or activation of nuclear materials, it is often difficult or too expensive to remove and dispose of all of the contaminated components. The desired approach is to decontaminate the materials to a greenfield condition so that they can remain on site, or to at least a low level radioactive waste criteria to reduce the cost of disposal off site. For the purpose of this discussion a greenfield condition is a term used to identify an acceptable level of radiation that will permit a facility or component member to be released for unrestricted applications. Many of these facilities, e.g., nuclear power electrical generating facilities, have a large number of inaccessible components, such as system process and drain piping that are often deeply embedded in concrete. The decontamination process becomes particularly difficult under such circumstances when the piping has small diameters measuring two inches or less.
Copending application WE58905 describes a method for accessing and decontaminating small embedded and relatively inaccessible piping runs. A parallel problem exists in radiologically mapping or surveying these type of surfaces once they have been decontaminated to assure that any residual radioactive contamination is within acceptable levels. Accessibility is one of the issues that can be addressed by the methods described in the foregoing patent application. However, there are still other issues that have to be over come because the prior art sensors used for this purpose are generally not configured to access these type of areas, i.e., being capable of being drawn through small diameter clearances or traverse U-traps and elbow bends, due to their size or configuration. Also the degree of sensitivity of the prior art sensors has been an issue because of the small absolute values of radioactive contamination to be measured due to the size of the areas to be monitored. These types of problems are not necessarily unique to nuclear facilities, but are in a number of respects common among facilities experiencing other forms of contamination, e.g. chemical processing facilities.
Accordingly, it is an object of this invention to provide a method of monitoring that can provide an integrated reading that will confirm the greenfield status of remediated surface areas in confined locations. It is also an object of this invention to achieve that with a sensor that is capable of scaling sharp bends and U-traps in small diameter piping of 5.08 cm (two inches) or less.